The present invention relates to electric terminals, and more particularly to terminals of the type which include one or more conductor pins which project through and are secured to a metallic body portion by a hermetic seal for disposing the ends of the conductor pins on opposite sides of the body portion.
Hermetically sealed electric terminals provide an airtight electrical terminal for use in conjunction with hermetically sealed devices where leakage into or from such devices, by way of the terminals, is effectively precluded. For hermetically sealed electric terminals to function safely and effectively for its intended purpose, the terminals require that their conductor pins be electrically insulated from and hermetically sealed to the body portion through which they pass and that an optimum air path be established and thereafter maintained between adjacent portions of the pins and opposite sides of the body.
In a conventional hermetic terminal assembly, exemplified by U.S. Pat. No. 3,160,460 to Wyzenbeek, a straight, current carrying pin is fixed in place within a lip defining a hole in the terminal body by a fusible glass-to-metal seal. A resilient insulator is bonded to the face of the body beyond the extent of the glass-to-metal seal. The insulator includes outwardly projecting portions bonded to the conductor pins which define a predetermined air path between adjacent portions of the pins and the body member. Such a hermetic terminal construction has been the standard in the industry for four decades.
The primary object of the present invention is to provide a hermetic terminal assembly having conductor pins that are rigidly and hermetically secured to the body portion entirely by a resilient plastic which possesses the requisite materials properties, such as dielectric, moisture resistance, resistance to chemical breakdown, to provide for a hermetic seal. In addition to providing a hermetic seal between the conductor pins and the body, the same resilient plastic is bonded to the conductor pins to provide the desired air path between the pins and the face of the body portion.
Another object of the present invention is to provide such a terminal that is simple and economical to manufacture, such as by plastic injection molding.
The present invention provides a hermetic terminal assembly having a cup-shaped body portion with a generally flat bottom wall and at least one opening in the bottom wall defined by an annular lip. A current conducting terminal pin extends through each opening and beyond the lip on both ends of the body portion, the inner end of the terminal pin being on the dish side of the cup-shaped body portion, and the outer end of the terminal pin extending through and to the outer side of the body portion. A resilient plastic resin material is molded into place within the body portion and interlocks with the body portion and the terminal pins to fixedly secure the terminal pins in position relative to the body portion. The plastic resin material forms a hermetic seal between the terminal pin and the body portion. In addition, the plastic extends beyond the face of the body portion and covers the pin to provide the desired air path between the respective pins and each other and/or the face of the body portion.
In alternate embodiments of the present invention, the terminal pins include shank portions with varying surface configurations that are intended to enhance the bonding of the plastic resin to the terminal pin and improve the hermeticity of the seal. The terminal pins may also include fuse portions that are intended to open in response to predetermined current loads seen at the terminal pins.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.